EXCHANGE 


UNIVERSITY  OF  PENNSYLVANIA 


I.    TUNGSTEN  HEXABROMIDE, 
II.    TUNGSTEN  COMPLEXES. 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL  OF  THE 

UNIVERSITY  OF  PENNSYLVANIA  IN  PARTIAL  FULFILLMENT 

OF  THE  REQUIREMENTS  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 

HARRY  BECKERMAN 


PHILADELPHIA,   PA. 
1918 


UNIVERSITY  OF  PENNSYLVANIA 


I.    TUNGSTEN   HEXABROMIDE. 
II.    TUNGSTEN  COMPLEXES. 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL  OF  THE 

UNIVERSITY  OF  PENNSYLVANIA  IN  PARTIAL  FULFILLMENT 

OF  THE  REQUIREMENTS  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 

HARRY  BECKERMAN 


PHILADELPHIA,   PA. 
1918 


ACKNOWLEDGMENT. 

The  author  desires  to  express  his  sincere  thanks  to  DR. 
EDGAR  F.  SMITH,  under  whose  direction  and  kindly  encourage- 
ment this  work  was  carried  out. 


I.    TUNGSTEN  HEXABROMIDE. 

INTRODUCTION. 

In  1851,  v.  Borch1  passed  bromine  over  highly  heated  tung- 
sten and  obtained  tungsten  pentabromide.  In  1857,  Riche*,2 
employing  the  same  reaction,  obtained  what  he  believed  to  be 
tungsten  hexabromide,  submitting,  however,  no  analyses  to 
support  his  belief.  In  1861,  Bloomstrand3  repeated  the  work 
of  Riche  and  showed  that  the  conditions  outlined  by  the  latter 
yielded  pentabromide  and  not  hexabromide.  In  1872,  Roscoe4, 
in  an  endeavor  to  prepare  tungsten  hexabromide,  acted  upon 
metallic  tungsten  with  bromine  at  a  red  heat,  in  an  atmosphere 
of  carbon  dioxide,  and  obtained  tungsten  pentabromide.  Tung- 
sten hexabromide  was  first  prepared  in  this  laboratory,  in  1896, 
by  Schaffef  and  Smith,5  by  allowing  bromine  to  act  on  tungsten 
metal  at  a  gentle  heat,  in  an  atmosphere  of  nitrogen.  These 
investigators  attributed  their  success  in  the  preparation,  to  the 
low  temperatures  at  which  they  operated,  the  high  temperatures, 
previously  employed,  tending  to  prevent  the  formation  of  hexa- 
bromide. They  also  replaced  the  carbon  dioxide  by  nitrogen, 
fearing  that  the  former  would  be  deoxidized  in  the  reaction  with 
the  formation  of  oxybromides.  The  amount  of  tungsten  hexa- 
bromide obtained,  however,  was  small  and  the  two  complete 
analyses  of  the  product  were  not  very  concordant.  As  a  conse- 
quence, a  confirmation  of  this  work  seemed  highly  desirable. 
The  purpose  of  the  present  investigation  was  to  confirm  the 
existence  of  tungsten  hexabromide  as  well  as  to  determine  more 
exactly  the  conditions  under  which  it  is  formed. 

In  1916,  Hill,6  in  this  laboratory,  noticed  that  the  action  of 
chlorine  on  tungsten  metal  to  form  tungsten  hexachloride  is 

'Oefvers.    af.    k.    Vetensk.    Akad.    Forh.    1851,    150.— Handbuch    der 
anorganischen  Chemie,  1912  (Gmelin-Kraut)  111,  I,  762. 

2  Ann.  Chim.  Phys.  (3)  50  (1857)  24. 

3  Jour.  pr.  ch.  82,  429. 

4  Ann.  der.  chem.  162,  362. 

5  Am.  Ch.  Jour.  18  (1896),  1098. 

6  Jour.  Am.  Chem.  Soc.  38  (1916),  2383. 

(3) 


catalyzed  to  a  remarkable  degree  by  the  presence  of  a  small 
amount  of  platinum  black.  The  temperature  of  formation  of 
tungsten  hexachloride  was  reduced  and  the  speed  of  reaction 
was  increased.  The  idea  presented  itself  that  this  method  applied 
to  the  preparation  of  tungsten  hexabromide  might  so  far  facilitate 
its  formation  that  a  good  yield  of  this  body  might  be  obtained. 


EXPERIMENTAL  PART. 

MATERIALS. 

The  best  results  were  obtained  with  a  finely  divided  tung- 
sten, formed  by  heating  tungsten  trioxide  in  hydrogen  for  a  long 
time,  at  as  low  a  temperature  as  possible,  care  being  taken  that 
the  metal  was  entirely  reduced.  The  tungsten  formed  in  this 
way  is  black  in  color  and  is  more  finely  divided  than  the  grey 
variety.  The  metal  was  not  permitted  to  remain  in  contact 
with  the  air  because  it  absorbs  both  oxygen  and  moisture.  It 
was  preserved  in  dry  hydrogen. 

The  bromine  used  was  prepared  by  treating  ordinary  bromine 
with  potassium  bromide  and  manganese  dioxide,  to  remove 
chlorine  and  organic  matter.  This  mixture  was  allowed  to  stand 
over  night,  and  the  bromine  was  then  distilled  out.  It  was 
washed  three  times  with  distilled  water  and  then  treated  with 
fused  CaCl2  over  night  and  distilled  again.  The  treatment 
with  fused  calcium  chloride  and  the  distillation  were  repeated 
twice.  The  distillation  of  the  bromine  took  place  entirely  in 
glass.  The  bromine  was  preserved  in  well  stoppered  bottles 
in  a  desiccator  over  concentrated  sulphuric  acid. 

Since  platinum  black  absorbs  oxygen  from  the  air,  it  was 
mixed  with  the  tungsten  trioxide  before  the  latter  was  reduced  in 
hydrogen.  The  tungsten  formed  was  thus  intimately  mixed 
with  the  platinum  and  was  entirely  free  of  oxygen. 

PROCEDURE. 

The  preparation  of  tungsten  hexabromide  is  very  difficult. 
Unless  the  greatest  possible  attention  is  paid  to  every  minute 
detail,  no  hope  for  success  can  be  entertained.  The  greatest 


difficulty  experienced  was  the  elimination  of  small  traces  of 
oxygen  which  leaked  into  the  apparatus,  in  spite  of  precautions 
taken  to  prevent  it.  This  trace  of  oxygen  was  removed  by  plac- 
ing in  the  tube  A,  before  the  boat  E,  a  long  layer  of  sugar  carbon. 
This  was  heated  to  redness.  The  carbon  dioxide  formed,  being 
diluted  with  a  large  quantity  of  nitrogen,  passed  on  without 
entering  the  reaction.  Sugar  carbon  made  by  heating  pure 
cane  sugar  contains  oxygenated  organic  bodies,  even  when  the 
carbon  is  heated  to  redness  in  a  blast  lamp.  These  oxygenated 
organic  bodies  were  removed  by  heating  the  carbon  to  a  high 
temperature  in  bromine  vapor  until  moisture  and  liquid  brominated 
bodies  were  no  longer  given  off.  The  sugar  carbon  was  then 
heated  in  dry  hydrogen  and  preserved  in  that  gas. 

The  character  of  the  tungsten  used  is  vital  to  the  success 
of  the  preparation.  Black  tungsten  proved  successful,  the  grey 
variety  giving  mostly  tungsten  pentabromide  mixed  with  a 
little  tungsten  hexabromide. 

The  air  was  displaced  from  the  apparatus  by  means  of  a 
stream  of  nitrogen  which  was  made  as  follows.  Air  was  forced 
by  means  of  a  water  blast  through  potassium  hydroxide  solution, 
to  remove  carbon  dioxide,  then  through  two  wash  bottles  con- 
taining concentrated  ammonia  water.  The  air  took  up  ammonia 
gas  and  then  passed  into  a  long  Jena  tube  containing  red-hot 
copper.  The  hydrogen  of  the  ammonia  combined  with  the 
oxygen  of  the  air  to  form  water.  The  latter  was  condensed  in  an 
empty  cooled  flask.  The  nitrogen  from  the  air  and  that  from 
the  ammonia  passed  into  another  Jena  tube  containing  a  red- 
hot,  reduced  copper  spiral,  to  remove  the  last  traces  of  oxygen. 
The  gas  was  then  washed  through  two  bottles  of  dilute  sulphuric 
acid  to  remove  traces  of  ammonia  which  might  still  be  retained 
by  the  nitrogen.  The  rest  of  the  apparatus  is  as  pictured  in 
Fig.  1 .  Moist  chromous  acetate  mixed  with  glass  beads  removed 
the  last  traces  of  oxygen.  From  here  on,  the  apparatus  was 
made  entirely  of  glass,  no  rubber  connections  or  stoppers  being 
used. 

The  nitrogen  was  thoroughly  dried  by  passage  through 
boiled  sulphuric  acid,  solid  potassium  hydroxide  and  phosphorus 
pentoxide.  The  gas  then  passed  through  the  U-tubes,  F  and  G, 
and  then  into  the  tube  A.  After  the  tube  A  was  placed  an  empty 


i 


0* 
CD 


CQ 


D 


7 

tower  to  condense  the  excess  of  bromine,  a  tower  with  fused 
CaCl2  and  then  a  vessel  containing  soda  lime  to  prevent  the 
bromine  vapor  from  reaching  the  air. 

A  porcelain  boat  containing  the  tungsten,  mixed  with  a 
trace  of  platinum,  was  removed  from  the  tube  in  which  it  was 
reduced  in  hydrogen.  It  was  quickly  inserted  into  the  tube  A 
through  the  ground-glass  joint  B.  A  plug  of  dried  glass  wool 
was  inserted  and  then  the  tube  was  filled  from  C  to  D  with  sugar 
carbon.  The  ground  glass  connection  B  was  shut  and  tightly 
clamped  by  means  of  rubber  bands.  It  was  coated  with  paraffine 
on  the  outside.  The  current  of  dry  nitrogen  was  continued  for 
eight  hours  more  to  remove  the  air  and  thoroughly  dry  the 
apparatus. 

The  sugar  carbon  was  heated  to  redness.  Bromine  was 
then  allowed  to  drop  from  the  separatory  funnel  H  into  the 
U-tube  F,  from  which  it  passed  into  G.  G  contained  glass  wool 
moistened  with  boiled  sulphuric  acid  to  remove  traces  of  moisture 
which  might  be  introduced  by  the  bromine.  F  and  G  were 
immersed  in  a  beaker  of  hot  water.  When  an  excess  of  bromine 
had  reached  the  porcelain  boat,  E,  the  latter  was  gently  heated. 
An  excess  of  bromine  was  maintained  at  the  moment  of  formation, 
otherwise  tungsten  pentabromide  would  have  been  formed. 
The  latter  does  not  combine  with  more  bromine  and  stays  as 
tungsten  pentabromide.  The  temperature  of  the  tube  at  E 
was  ascertained  by  placing  a  thermometer  in  contact  with  it. 
The  reaction  started  at  200°  C.  At  230°  C.  it  was  fairly  rapid. 
The  tungsten  hexabromide  rose  from  the  boat  in  the  form  of  a 
heavy  reddish  brown  vapor  which  condensed  in  the  colder  part 
of  the  tube  to  a  reddish  brown  liquid.  The  latter  on  cooling 
solidified  with  a  crackling  sound,  forming  a  crystalline  solid. 
The  first  portion  was  driven  beyond  the  point  at  which  it  was 
intended  to  collect  the  main  part  of  the  preparation.  The 
remainder  was  fractionally  redistilled  in  an  excess  of  bromine 
vapor.  A  non-volatile  black  residue  was  left  behind.  The 
middle  fraction  was  collected  between  two  constrictions.  After 
cooling,  the  excess  bromine  was  removed  by  means  of  the  stream 
of  nitrogen.  The  bulb  containing  the  preparation  was  then 
sealed  off. 


8 

Tungsten  hexabromide  is  a  blue-black  crystalline  solid 
which  can,  with  care,  be  sublimed  in  bromine  vapor  in  the  form 
of  blue-black  shining  needles.  It  appears  to  be  soluble  in  liquid 
bromine.  It  fumes  in  the  air.  Water  decomposes  it  giving  a 
deep  blue  oxide.  Ammonium  hydroxide  dissolves  it  completely. 
Concentrated  sulphuric  acid  and  concentrated  nitric  acid  form 
tungstic  oxide.  On  heating  it  evolves  bromine. 


METHOD   OF  ANALYSIS. 

TUNGSTEN  CONTENT. 

A  porcelain  crucible  containing  a  weighed  portion  of  the 
preparation  was  placed  in  a  covered  beaker  containing  a  little 
warm  water.  The  water  vapor  acted  rapidly  on  the  preparation, 
decomposing  it,  without  causing  it  to  spatter.  The  mass  liquified. 
The  crucible  was  then  placed  on  a  stove  plate  and  the  contents 
carefully  evaporated  to  dryness.  Dilute  nitric  acid  was  added 
and  again  evaporated  to  dryness.  Moderately  concentrated  nitric 
acid  was  added;  then  finally  concentrated  nitric  acid  was  added 
repeatedly,  evaporating  to  dryness  each  time.  The  tungsten 
trioxide  so  formed  was  ignited  and  weighed. 

BROMINE  CONTENT. 

A  weighed  sample  was  placed  in  a  Bunsen  apparatus.  Nitric 
acid  was  added  by  means  of  a  separatory  funnel  fused  into  the 
delivery  tube  of  the  flask.  The  mixture  was  distilled  into  silver 
nitrate  solution.  The  distillate,  containing  silver  bromide, 
silver  bromate  and  excess  of  silver  nitrate,  was  transferred  to  a 
porcelain  dish  and  evaporated  to  dryness.  The  residue  was 
ignited  to  change  the  silver  bromate  to  silver  bromide.  The 
dish  was  allowed  to  cool.  Nitric  acid  was  added  and  then  hot 
distilled  water  containing  a  little  nitric  acid.  The  silver  bromide 
was  filtered  and  washed.  It  was  weighed  as  silver  bromide. 
The  results  are  given  in  Table  I. 


TABLE  I. 


Preparation  No.  9. 


Wt.  of  Sample. 

Wt.  of  W03. 

%w. 

0.1023  gr. 

0.0366gr.  WO3 

28.35  W 

0.4126    " 

0.1492    "      " 

28.67    " 

0.2156    " 

0.0774    "      " 

28.43    " 

0.4249    " 

0.1528    "      " 

28.53    " 

0.5236 


0.8834    "  AgBr 


Preparation  No.  12. 

Wt.  of  Sample.  Wt.  of  WO3. 

0.  1575  gr.         0.0554gr.  WO3 


0.8152  ' 

0.0698  " 

0.6354  " 

0.4582  " 


0.2882  " 

0.0243  "      " 

/0. 2243  "      " 

{  1.0735  "  AgBr 

0.1623  "    WO3 

0.7730  "  AgBr 


27.87 
28.04 
27.65 

28.00 


28.09 


Theoretical  Percentages. 


%Br. 


71.79  Br 


%Br. 


WBr5. 
31.52  W 
68.48  Br 


WBr«. 
27.72  W 
72.28  Br 


71.89 


71.80 


THE    ACTION     OF     CHLORINE    AND     BROMINE     ON 
MOLYBDENUM  MIXED  WITH  PLATINUM  BLACK. 

The  success  attained  with  the  preparation  of  tungsten 
hexabromide  raised  the  hope  that  platinum  black  would  cata- 
lyze the  reaction  between  chlorine  and  molybdenum.  Chlorine 
acts  on  molybdenum  metal  at  a  dull  red  heat  to  form  molyb- 
denum pentachloride.  It  was  thought  that  the  temperature  of 
formation  would  be  reduced  so  that  molybdenum  hexachloride 
might  be  formed.  The  latter  has  never  been  obtained. 

Finely  divided  molybdenum  was  mixed  with  platinum 
black  and  was  subjected  to  the  action  of  chlorine  in  an  atmosphere 
of  nitrogen.  The  action  started  at  40°  C.  Unless  the  chlorine 
was  diluted  with  a  large  quantity  of  nitrogen,  the  reaction  became 
so  violent  that  the  metal  caught  fire  in  the  chlorine.  The  action 
was  allowed  to  proceed  slowly  at  50°  to  60°  C.  Large,  black, 
highly  lustrous  crystals  formed  in  the  boat.  These  were  slowly 
sublimed  out,  collected  between  two  constrictions  and  sealed 
up  in  glass.  They  were  analyzed  by  the  method  described  under 


id 

tungsten  hexabromide.  Care  was  taken  to  prevent  volatilization 
of  the  molybdenum  trioxide,  by  careful  ignition.  The  results 
are  given  in  Table  II. 

TABLE  II. 

Theoretical  Percentages. 
Wt.  of  Sample.  Wt.  of  MoOa.  %  Mo.  %  Cl.  MoCU.  MoCl«. 

0.2065gr.  0.1083gr.  34.96  35. 13  Mo         31. 09  Mo 

0.1843    "  0.0976    "  35.33  64.87  Cl  68.91  Cl 

0.5168    "  0.2734    "  35.26 

0.1519    "  0.0799    "  35.02 

„        fo.3875    "  35.32 

\  1.9445    "  AgCl  65.75 

Average  Mo  35. 18 
The  compound,  therefore,  was  molybdenum  pentachloride. 


Molybdenum  pentabromide  has  never  been  made.  Indeed, 
molybdenum  tetrabromide  is  difficult  to  prepare,  it  being  formed 
in  small  traces  when  bromine  is  passed  over  molybdenum,  the 
chief  product  being  molybdenum  tribromide.  Attention  was 
next  directed  to  the  preparation  of  molybdenum  pentabromide. 

Molybdenum  metal,  mixed  with  platinum  black,  was  heated 
in  Br  vapor.  At  130°  to  140°  C.,  the  reaction  proceeded  rapidly. 
Long,  sharp,  hairy  needles  formed  above  the  boat.  On  resublim- 
ing  they  decomposed  into  yellow  Mo  Br2.  Therefore  the  boat 
was  removed  from  the  tube,  the  crystals  were  quickly  detached 
and  dropped  into  a  weighing  bottle.  The  substance  was  very 
voluminous,  a  large  bulk  of  the  hairy  crystals  weighing  very  little. 

TABLE  III. 

Theoretical  Percentages. 

Wt.  of  Sample.        Wt.  of  MoOs.  %  Mo.  MoBn.  MoBrs. 

0.0431gr.  0.0155gr.  23.89  23. 08  Mo  19. 36  Mo 

The  substance,  therefore,  was  MoBr4. 


II.    TUNGSTEN  COMPLEXES. 

INTRODUCTION. 

Inorganic  complexes  play  a  more  important  role  than  is 
generally  believed  to  be  the  case.  The  difficulty  which  is  fre- 
quently met  with,  in  the  purification  of  substances  can,  often, 
be  directly  attributed  to  the  formation  of  complexes.  For 
example,  Smith  and  Exner1  in  an  exhaustive  paper  on  the 
atomic  weight  of  tungsten  show  conclusively  that  the  difficulty 
of  preparing  pure  tungstic  acid  is  due  to  the  ease  with  which 
the  latter  substance  forms  complexes.  They  found  that  on 
digesting  tungstic  acid,  which  was  free  of  iron,  with  hydrochloric 
acid  or  nitric  acid,  in  which  iron  was  present,  the  latter  would 
enter  the  tungstic  acid.  Iron,  manganese,  phosphorus  and 
vanadium  were  extremely  difficult  to  remove.  Indeed  an 
ammonium  salt  of  a  complex,  containing  the  oxides  of  the  above 
elements,  was  isolated.  Similarly,  the  slimy,  greenish  or  bluish 
white  residue  remaining  when  tungstic  acid  dissolved  in  ammonium 
hydroxide,  was  found  by  them  to  contain  ammonium  chloride. 
It  was  probably  an  ammonium  chlorinated  tungstic  acid  derivative. 

Again,  Rogers  and  Smith2  have  shown  that  the  introduction 
of  only  a  few  tenths  of  one  per  cent  of  various  dioxides,  like 
TiO2  and  ZrO2,  into  ammonium  vanadico-phospho-tungstate 
changed  its  properties  and  reactions  entirely.  The  authors 
point  out  that  in  mineral  analysis  the  influence  of  such  minute 
amounts  of  supposedly  foreign  constituents  is  too  often  dis- 
regarded and  not  considered  in  the  deduction  of  formulas. 

As  a  consequence  an  intimate  knowledge  of  complexes, 
the  conditions  under  which  they  are  formed,  their  analyses, 
are  subjects  of  importance.  The  purpose  of  the  present  investi- 
gation is  to  continue  the  study  of  complexes  which  has  been 
carried  on  in  this  laboratory  for  a  number  of  years. 

In  1895,  Wolcott  Gibbs,3  the  pioneer  in  this  field  of  research, 

1  Proc.  Am.  Phil.  Soc.  43  (1904),  123. 

2  Jour.  Am.  Chem.  Soc.  25  (1903),  1223. 

3  Am.  Chem.  Jour.  17  (1895),  173. 

(11) 


12 

prepared  complexes  containing  molybdenum  dioxide  by  boiling 
hydrated  MoO2  with  sodium  para  tungstate.  From  the  deep 
orange  colored  solution,  potassium  bromide  gave  a  buff  colored 
precipitate  which  was  recrystallized  from  water  in  small  pale 
brown  scales.  Gibbs  ascribed  the  formula  5  K2O.MoO2. 12  WCV 
16  H2O  to  the  compound.  It  was  thought  that  corresponding 
complexes  containing  tungsten  dioxide  might  exist. 


EXPERIMENTAL. 

The  reduction  of  hydrated,  precipitated  tungsten  trioxide 
to  hydrated  tungsten  dioxide  by  zinc  and  hydrochloric  acid 
was  found  to  be  a  difficult  task.  After  five  days'  action,  the 
reduction  had  not  reached  the  tungsten  dioxide  stage.  Several 
known  methods  were  tried  and  the  best  was  found  to  be  the 
following:  A  large  excess  of  tungsten  trioxide  was  boiled  up 
with  sodium  hydroxide  solution.  A  small  test  portion  of  the 
solution  was  treated  from  time  to  time  with  dilute  hydrochloric 
acid  until  a  precipitate  of  tungstic  acid  no  longer  formed.  This 
indicated  the  formation  of  a  meta  tungstate,  Na2O.4WO3. 
The  solution  was  filtered.  Zinc  dust,  added  to  this  solution, 
turned  it  intense  indigo  blue.  Dilute  hydrochloric  acid  was 
then  added.  In  a  few  minutes  copper-red,  hydrated  tungsten 
dioxide  formed.  The  increased  speed  of  the  reduction  was  due 
to  the  fact  that  the  action  took  place  in  solution  instead  of  in 
the  solid  phase.  The  tungsten  dioxide  was  filtered  and  washed 
on  the  suction  pump  in  an  atmosphere  of  hydrogen. 

I.  Ammonium  para  tungstate,  dissolved  in  water,  was 
boiled  up  with  the  hydrated  tungsten  dioxide.  A  deep  blue 
solution  formed.  The  excess  tungsten  dioxide  was  filtered  out 
carefully.  On  standing  the  solution  turned  bright  green  and 
then  deep  orange  colored.  The  same  changes  in  color  took  place 
in  an  atmosphere  of  hydrogen,  so  that  the  change  was  not  due  to 
oxidation.  On  heating,  the  orange  colored  solution  changed 
back  to  green  and  then  to  deep  blue.  Potassium  iodide,  added 
in  large  excess,  gave  a  buff  colored  precipitate.  This  was  filtered 
out.  It  was  soluble  in  hot  water,  difficultly  soluble  in  cold. 


13 

It  was  recrystallized  from  water,  coming  down  in  beautiful  light 
brown  crystals.  Sodium  bromide,  added  to  the  orange  colored 
solution,  gave  the  light  brown  sodium  salt.  The  similarity  to 
the  MoO2  compounds  obtained  by  Gibbs  is  marked.  Lead 
acetate  gave  a  heavy  yellowish  white  crystalline  precipitate. 
Silver  nitrate  gave  a  red  precipitate,  somewhat  soluble  in  hot 
water  giving  a  red  solution.  Mercurous  nitrate  gave  a  reddish 
brown  precipitate.  Alcohol  threw  down  the  brown  alkali  salt. 
Manganous  sulphate  gave  a  white  precipitate.  The  cobalt  salt 
was  rose  colored,  while  a  copper  compound,  precipitated  by 
copper  sulphate,  was  greenish  yellow.  Ferric  chloride  gave  no 
precipitate.  The  barium  salt  was  white. 

ANALYSIS   OF  THE   POTASSIUM   SALT. 

WO2  CONTENT. 

A  weighed  portion  was  dissolved  in  water.  Dilute  sulphuric 
acid  was  added  and  then  an  excess  of  standard  potassium  per- 
manganate solution.  The  solution  was  warmed  on  the  water 
bath.  It  was  then  cooled  and  an  excess  of  ferrous  ammonium 
sulphate,  dissolved  in  water,  was  added.  The  excess  ferrous 
iron  was  titrated  back  with  potassium  permanganate  solution. 
The  tungsten  dioxide  content  was  calculated. 

AND  KzO  CONTENT. 


The  complex  was  found  to  be  only  slowly  decomposed  by 
concentrated  nitric  acid  or  aqua  regia.  .  The  following  method 
proved  satisfactory.  A  weighed  sample  was  dissolved  in  hot 
water.  A  few  cubic  centimeters  of  dilute  sulphuric  acid  and  a 
little  nitric  acid  were  added.  The  solution  was  evaporated,  in 
an  air  bath,  to  strong  fumes.  After  cooling,  water  was  added 
and  the  evaporation  to  fumes  repeated.  Nitric  acid  and  water 
were  added  and  the  mixture  was  digested  for  one  hour.  The 
tungsten  trioxide  was  filtered  out  and  washed  with  hot  water 
containing  nitric  acid.  It  was  then  ignited  and  weighed.  The 
filtrate  from  the  WOa  was  evaporated  to  small  bulk,  transfered 
to  a  weighed  crucible.  The  evaporation  was  continued,  the  sul- 
phuric acid  was  driven  off.  The  potassium  sulphate  was  ignited 


14 


and  weighed.      The  water  was  obtained   by  difference.       The 
results  are  contained  in  Table  4. 

TABLE  IV. 

Theoretical   %  calculated  for 
Wt.  of  Complex.     Wt.  of  Constituent  Found.  %  5  KzO. WO2. 12  WOs.  13  HiO. 

0.3072gm.  0.0184gr.  WO2  5.99WO2                  5.83WO2 

0.4664     "  0.0271    "  "  5.81     " 

0.3282     "  0.2465    "  WO3  75 .  1 1  WO3                 75.16WO3 

0.3236     "  0.2417    "  "  74.69     " 

0.3282     "  0.0762    "  K2SO4  12.55  K2O                 12.69  K2O 

0.3236     "  0.0768    "  ':  12.82     " 

by  difference  6.52  H2O  6.32H2O 

The  above  analysis  shows  the  complex  to  be 
5  K2O. WO2. 12  WO3. 13  H2O. 

The  analysis  of  the  sodium  derivative  is  given  in  Table  V. 
TABLE  V. 

Theoretical   %  calculated  for 
Wt.  of  Complex.     Wt.  of  Constituent  Found.  %  5  Na2O.WOz.  12  WOs.24  H2O. 

0.2293gr.  0.0135gr.  WO2  5.89WO2  5.77WO2 

0.5062    "  0.0287  gr.     "  5.67  " 

0.2646    "  0.1969    "    WO3  74.41  WO3  74.40  WO3 

0.2035  "  0.1508  "   "  74.10  " 

0.2646    "  0.0508   "    Na2SO4  8.39  Na2O  8.29  Na2O 

0.2035    "  0.0382    "      "  8.21     " 

by  difference  11.67H2O  11.54H2O 

The  complex,  therefore,  is 

5  Na2O.WO2.12  WOs-24  H2O. 

II.  In  an  attempt  to  repeat  the  preparation  of  the  potassium 
complex,  the  ammonium  para  tungstate  solution  was  boiled 
up  with  the  hydrated  tungsten  dioxide  for  a  much  longer  time 
than  in  the  first  preparation.  Potassium  iodide,  added  to  the 
solution,  gave  a  deep  brown  precipitate,  instead  of  the  buff 
colored  precipitate  obtained  previously.  On  recrystallizing  from 
water,  the  difficultly  soluble  light  brown  complex,  obtained 
before,  crystallized  out  first.  This  was  followed  by  dark  brown 


15 

crystals.  The  latter  were  much  more  soluble  in  water  and  could 
easily  be  separated  from  the  light  brown  crystals  by  several 
recrystallizations.  The  mother  liquor  from  the  first  preparation 
of  the  light  brown  compound  was  deep  brown  in  color  and 
probably  contained  this  new  body.  The  dark  brown  crystals 
were  analyzed  as  outlined  before. 

TABLE  VI. 

Theoretical   %  calculated  for 
Wt.  of  Complex.     Wt.  of  Constituent  Found.  %  5  K2O.2  WO2. 12  WOs.  11  HjO. 

0.8765gr.  0.0995gr.  WO2  11.35WO2  11.12WO2 

0.4966    "  0.0552    "      "  11.12     " 

0.2111    "  0.1514   "    WO3  71.72  WO3  71.68WO3 

a.5199    "  0.3716    "      "  71.48     " 

0.2111    "  0.0471    "    K2SO4  12.03  K2O  12.10K2O 

0.5199    "  0.1164    "      "  12.09     " 

by  difference     5.11  H2O  5.10  H2O 

The  formula  of  the  dark  brown  crystals  as  deduced  from  the 
above  analysis,  therefore,  is 

5  K2O.2  WO2.12  WOs.ll  H2O. 

Lead  acetate  added  to  a  solution  of  the  potassium  salt  gave 
a  heavy  white  precipitate.  Mercurous  nitrate  gave  a  green 
precipitate.  The  ferric  salt  was  yellow.  Silver  nitrate  gave  a 
chocolate  colored  precipitate.  On  boiling,  the  latter  darkened. 
This  was  soluble  in  ammonium  hydroxide  leaving  metallic  silver. 
The  cobalt  salt  was  pink.  Copper  sulphate  gave  a  greenish  white 
precipitate. 


III.  Sodium  metatungstate,  Na2O.4  WO3. 10  H2O,  was  dis- 
solved in  water.  To  this  solution  hydrated  tungsten  dioxide 
was  added  and  the  solution  was  boiled  for  some  time.  The 
excess  tungsten  dioxide  was  filtered  from  the  deep  blue  solution. 
On  standing  the  solution  turned  green  and  then  orange  colored. 
The  compound  would  not  crystallize  out,  on  concentrating  and 
cooling  the  solution.  It  was  isolated  by  adding  alcohol,  when 
it  settled  as  a  brown  oil.  The  latter  was  separated  and  warmed 
gently  in  hydrogen  to  dry  it.  It  soon  solidified  as  a  white  crystal- 


16 

line  solid.      It  was  soluble  in  water  giving  an  orange  colored 
solution.     The  analysis  of  the  sodium  compound  follows: 


Wt.  of  Complex. 

Wt.  of  Constituent  Found.             % 

0.3654gr. 

0.0141  g 

r.  WO2 

3.86  WO2 

0.3087    " 

0.0122   ' 

(      «t 

3.95     " 

0.7645    " 

0.0286    ' 

<      « 

3.74     " 

0.2760    " 

0.2297    ' 

'    WO3 

83.22  W03 

0.2472    " 

0.2052    ' 

«       « 

83.01     " 

0.4334    " 

0.3615    ' 

'      " 

83.41     " 

0.2760    " 

0.0357    ' 

'    Na2S04 

5.65  Na2O 

0.2472    " 

0.0321    ' 

»      « 

5.67     " 

0.4334    " 

0.0543    ' 

4              l« 

5.47     " 

by 

difference 

7.38  H2O 

TABLE  VII. 

Theoretical  %  calculated  for 
5  NazO.WOt.20  WO3.23  H2O. 

3.85   WOj 
83.15  WO, 
5.55  Na2O 

7.45  H,O 

The  analysis  indicates  the  formula  to  be 

5  Na2O.W02.20  WO3-23  H2O. 

Lead  acetate  formed  a  heavy  white  precipitate.  Mercurous 
nitrate  gave  a  yellow- white  precipitate,  while  that  formed  by 
silver  nitrate  was  purple  colored,  insoluble  in  hot  or  cold  water. 
Ferric  chloride  gave  an  orange  colored  precipitate.  Potassium 
iodide  added  to  a  cooled  solution  of  the  sodium  salt,  gave  the 
less  soluble  potassium  salt  of  the  complex  in  long  colorless  crystals. 

IV.  Pechard1  has  shown  that  when  sulphur  dioxide  is  passed 
into  a  solution  of  ordinary  ammonium  molybdate,  compounds 
are  formed  which  conform  to  the  formula,  4(NH4)2O.3  SO2. 
10MoO3-6H20.  It  was  thought  that  corresponding  tungsten 
complexes  might  exist.  Accordingly  ammonium  paratungstate 
was  dissolved  in  water  and  sulphur  dioxide  was  passed  in.  The 
gas  was  rapidly  absorbed.  The  solution  was  concentrated  by 
evaporating  on  the  water  bath,  sulphur  dioxide  being  passed 
through  the  solution,  during  the  evaporation,  to  keep  it  saturated 
with  the  gas.  On  cooling  in  ice  water,  large  colorless  octahedrons 
formed.  Some  of  the  crystals  were  fully  three-quarters  of  an 
inch  across.  They  were  extremely  soluble  in  water.  The  com- 

1  Compte  Rendus  116,  1441  (1893). 


17 

pound  was  recrystallized  several  times  from  water.  Analysis 
showed  no  sulphur  dioxide  to  be  present  in  the  compound.  It 
proved  to  be  ammonium  metatungstate,  (NH4)2O.4  WOa.8  H2O. 


TABLE  VIII. 

Theoretical  %  calculated  for 
Wt.  of  Compound.     Wt.  of  Constituent  Found.  %  (NH4)zO.4  WOa.8  HjO. 

0.3014gr.         0.0166gr.  (NH4)2O       5.52(NH4)2O  4.63  (NH4)2O 

0.5752    "  0.0315    "      "  5.47     " 

0.3424   "          0.2858   "   WO3  83.47WO3  82.56WO3 

0.4598    "  0.3836   "      "  83.43     " 

by  difference  11.15  H2O  12.81  H2O 

This  reaction  constitutes  a  rather  quick  and  easy  method 
for  the  preparation  of  ammonium  metatungstate. 


V.  Titanium  hydroxide,  made  by  adding  redistilled 
ammonium  hydroxide  to  a  solution  of  potassium  titanium 
fluoride,  and  zirconium  hydroxide,  made  by  adding  ammonium 
hydroxide  to  a  solution  of  zirconium  sulphate,  were  boiled  up 
separately  with  a  solution  of  potassium  paratungstate  for  several 
hours.  The  excess  titanium  and  zirconium  hydroxides  were 
filtered  out  in  each  case  and  the  complexes  were  crystallized. 
They  were  analyzed  by  precipitating  titanium  and  zirconium 
hydroxides  with  ammonium  hydroxide  and  weighing  them  as 
dioxides.  The  tungsten  trioxide  and  potassium  sulphate  were 
formed  as  outlined  before. 

TABLE  IX. 

Theoretical  %  calculated  for 
Wt.  of  Complex.     Wt.  of  Constituent  Found.  %  22  K2O.TiO2.57  WO3.39  HiO. 


0.3746gr. 

0.0019gr.  TiO2 

0.51  TiO2 

0.50  TiO2 

0.4282    " 

0.0021    "      " 

0.49     " 

0.3746    " 

0.3072    "   WO3 

82.01  WO3 

82.27  WO3 

0.4282    " 

0.3524   "      " 

82.30     " 

0.3746    " 

0.0901    "   K2SO4 

13.00  K2O 

12.87  K2O 

0.4282    " 

0.1016   "      " 

12.82     " 

by  difference      4.43  H2O  4.36  H2O 

22  K2O.TiO2.57  WO3.39  H2O. 


18 
TABLE  X. 


Theoretical   %  calculated  for 

Wt.  of  Complex. 

Wt.  of  Constituent  Found. 

% 

29K2O.Zr02.70W03 

.  73  H2O. 

0.3446gr. 

0.0019gr.  ZrO2 

0.55  ZrO2 

0.60ZrO2 

0.3767    " 

0.0024   "      " 

0.64     " 

0.3446   " 

0.2743    "  WO3 

79.60  WO3 

79.60  WO3 

0.3767    " 

0.2982    "      " 

79.17     " 

0.3446    " 

0.0834   "   K2SO4 

13.09K2O 

13.36K2O   , 

0.3767    " 

0.0975    "      " 

13.99     " 

by  difference       6 . 48  H2O  6 . 44  H2O 

29  K2O .  ZrO2 .  70  WO3 .  73  H2O. 

Had  the  zirconium  dioxide  content  been  only  0.13%  higher, 
then  the  formula  of  the  zirconium  dioxide  complex  would  have 
corresponded  exactly  to  the  formula  of  the  titanium  dioxide 
complex.  Both  the  ZrOz  and  the  TiC>2  complexes  were  white 
crystalline  solids,  soluble  in  hot  water. 

VI.  A  solution  of  potassium  paratungstate  was  boiled  up 
with  freshly  precipitated  lead  dioxide.  After  filtering  out  the 
excess  of  lead  dioxide,  the  complex  was  crystallized.  It  is  a 
crystalline  solid  with  a  faint  orange  tint,  soluble  in  water.  The 
compound  was  analyzed  by  adding  to  the  solution  of  a  weighed 
portion,  a  few  drops  of  alcohol  and  concentrated  nitric  acid. 
This  converted  the  lead  dioxide  to  lead  nitrate.  The  solution 
was  evaporated  to  dryness,  the  residue  was  baked  and  taken  up 
in  1  :  1  nitric  acid.  The  evaporation  and  baking  were  repeated 
twice.  Nitric  acid  was  added,  then  hot  water  containing  nitric 
acid.  The  tungsten  trioxide  was  filtered  out  and  weighed.  The 
filtrate  containing  lead  nitrate  and  potassium  nitrate  was  evapo- 
rated to  fumes  with  sulphuric  acid.  Water  and  alcohol  were 
added.  The  lead  sulphate  was  filtered  out  and  weighed.  The 
filtrate  was  evaporated  to  dryness  and  the  potassium  sulphate 
was  weighed. 


19 

TABLE  XI. 

Theoretical  %  calculated  for 

Wt.  of  Complex.     Wt.  of  Constituent  Found.  %          64  K2O.PbC>2  171  WO3. 1 19  HuO. 

0.3341  gr.         0 . 0022  gr.  PbSO4        0 . 5 1  Pb  O2  0.50  PbO2 

0.3294    "  0.0020    "      "  0.49    " 

0.3341    "  0.2763    "   WO3          82.70WO3  82.53WO3 

0.3294    "  0.2712    "      "  82.33    " 

0.3341    "          0.0772    "   K2SO4       12.5lK2O  12.52K2O 

0.3294    "  0.0767    "      "  12.57     " 

by  difference       4 . 44  H2O  4 . 45  H2O 

64  K2O.Pb02.  171  W03.  119  H2O. 

It  will  be  noticed  that  this  formula  is  just  three  times  the 
formula  of  the  titanium  dioxide  complex. 


SUMMARY. 

1.  The    existence    of    tungsten    hexabromide    is    confirmed. 
Exact  details  are  given  for  its  preparation  in  larger  quantities. 

2.  Platinum  black  will  catalyze  the  reaction  between  chlorine 
and  molybdenum  and  between   bromine   and  molybdenum   so 
that  the  formation  of  molybdenum  pentachloride  and  molyb- 
denum tetrabromide  is  facilitated. 

3.  The  formulas  of  the  following   complexes   were   derived 
from  their  analyses : 

5  K2O .  WO2 .  1 2  WO3 . 1 3  H2O     \  analogous  to  5K2O .  MoO2 .  1 2   WO3 .  1 6   H2O 
5  Na2O .  WO2 .  1 2  WO3 . 24  H2O   /      obtained  by  Wolcott  Gibbs. 
5  K2O.2  WO2.12  WOa.ll  H2O 
5  -Na20 .  WO2 .  20  WO3 .  23  H2O 

4.  The  following  ratios  were  also  obtained: 

22  K2O.TiO2.57  WO3.39  H2O 
29  K2O .  Zr02 .  70  WO3 .  73  H2O 
64  K2O .  PbO2 .171  WO3 .119  H2O 

5.  Sulphur    dioxide    acts    upon    ammonium    paratungstate 
removing  part  of  the  volatile   alkali   and  forming  ammonium 
metatungstate.     This  forms  a  convenient  method  for  the  prepara- 
tion of  the  latter  compound. 


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